12-inch Mark I.
12½-inch R. M. L. 38 Tons.
Introduced in 1875. There is but one mark of this calibre, and it exactly resembles the 35-ton 12-inch.
16-inch R. M. L. 80 Tons.
Introduced in 1878. There is but one mark of this calibre. These guns have a chamber one inch greater in diameter than the bore, and the form of rifling is that used with expanding projectiles, being multigroove with shallow grooves. The construction corresponds to the latest development of the Woolwich pattern.
16-inch.
Armstrong Construction.
The first type of rifled guns introduced into the English naval service was the Armstrong, for both breech and muzzle loaders. Fabrication of original breech-loader ceased in 1864, but many of this type still remain in service. The original construction of the muzzle-loader was modified in 1864, but the general type and principles were preserved and are still used. The present type of modified Armstrong construction is used by many foreign services, and the 100-ton gun has been introduced in the English service. The modified Armstrong breech-loading system for the 100-ton gun has been adopted in Italy.